Measurement of particulate matter, such as particulate matter entrained in a flow of gas, is important for a number of reasons. In the industrial setting, for example, government regulations specify permissible parameters for amounts of particulate matter that may be exhausted to the atmosphere. Non-extractive optical particulate monitors for these purposes are well known, however, improvement is desired.
The present invention relates to an improved non-extractive optical particulate monitor for measuring particulate matter entrained in a flow, such as a flow in a smokestack.
In a preferred embodiment, the monitor includes a light emission system which projects a beam of light into the smokestack. A light detection system is positioned laterally of the beam to receive and detect light scattered by the particulate matter in the smokestack. A calibration system is located between the light emission system and the light detection system. Light from the light emission system accesses the light detection system through the calibration system for calibration of the monitor without traveling through the flow structure.
In yet another aspect, the invention relates to a method for checking operating conditions of an optical monitor configured for monitoring particulate matter in a flow conduit. The steps include providing an optical monitor having a light source and a light detection system. The light detection system includes a collector lens having principal planes. Light is directed from the light source to the light detection system via a path that does not travel through the flow conduit. The light directed to the light detection system is directed in a plane approximately parallel to the principal planes of the collector lens to yield information corresponding to the cleanliness of the collector lens.
A significant advantage of the invention is that it is configured so that it can be mounted externally to a smokestack. Other advantages include minimization of exposed surfaces, simplification of moving parts, and identification of dirty monitor conditions.